1. Field of the Invention
The present invention relates to an optical module, and more particularly to an optical module including a printed circuit board (PCB) having a plurality of integrated photoelectric conversion devices and an optical axis alignment method.
2. Description of the Related Art
In general, PCBs have a structure that include copper wiring laminated on a plastic board made of epoxy resin, polyimide resin, or phenol resin. However, such PCBs are not suitable for high-speed, long-distance, communication devices. More specifically, communication devices connected by copper lines cannot easily transmit data with a high transmission rate of a few Gb/sec or more, even at short distances of tens of centimeters, due to high loss rate and noise generation.
Optical communication devices, which replace the copper lines by optical fiber lines, can be used to establish high-speed, long-distance, communication networks. Such optical communication networks use optical signals as a medium for data transmission and need an optical module including photoelectric conversion devices for generating optical signals from electric signals, as well as for receiving optical signals and outputting electric signals.
The conventional optical module includes a planar optical waveguide device, which is composed of waveguides for inputting/outputting optical signals, and a PCB glued on the planar optical waveguide device.
The PCB has integrated photoelectric conversion devices that generate and detect optical signals, as well as converting the optical signals into electric signals. The photoelectric conversion devices may include surface emission type light sources or surface reception type optical detection devices. In other words, the optical module needs devices for optically connecting the PCB to the planar optical waveguide device.
FIG. 1 shows the structure of a conventional optical connection block 100. The conventional optical connection block 100 includes a block 120, a plurality of optical fibers 110 mounted within the block 120 as a medium for transmitting/receiving optical signals, and a reflection layer 121 formed on an end of the block 120, which is processed to have a predetermined angle.
The block 120, which supports the optical fibers 110, has a plurality of V-grooves (not shown) formed thereon for holding and seating the optical fibers 110. The end of the block 120 is processed so that it has a predetermined angle.
The optical connection block 100 optically connects a PCB (not shown) formed on a planar optical waveguide (not shown) to the planar optical waveguide by processing an end of the block 120 with a predetermined angle and forming the reflection layer 121 on the processed surface.
As the planar optical waveguide, a PLC (planar lightwave circuit) including a plurality of waveguides manufactured by a semiconductor process or an optical fiber block including a plurality of optical fibers may be used. The PCB has integrated active optical conversion devices that convert optical signals into electric signals and vice versa.
FIG. 2 shows the construction of an optical system 200 that includes first and second optical modules 220 and 230, respectively. The optical modules 220 and 2230 are connected by an optical fiber 210. The first and second optical modules 220 and 230 include planar optical waveguides 221 and 231 and PCBs 222 and 232 positioned on the corresponding planar optical waveguides 221 and 231. The PCBs 222 and 232 have integrated photoelectric conversion devices that convert optical signals into electric signals or vice versa.
The optical fiber 210 connects the first and second optical modules 220 and 230 to each other.
However, conventional optical connection blocks have a problem in that they are difficult to manufacture. More specifically, it is difficult to process an end of the blocks in such a manner that it has an end surface slanted with a predetermined angle. If the angle of the processed end surface varies, the path of optical signals is changed, and noise and intensity loss occur.
In addition, conventional optical connection blocks have a bulky structure because the optical modules are integrated with optical fibers. This limits the application of the blocks to optical modules or optical communication systems that require a compact size.